Update actions/checkout from v2 to v3

lib/actions-util.js

@@ -455,7 +455,7 @@ async function getRef() {
         return ref;
     }
     const head = await (0, exports.getCommitOid)(checkoutPath, "HEAD");
-    // in actions/checkout@v2 we can check if git rev-parse HEAD == GITHUB_SHA
+    // in actions/checkout@v2+ we can check if git rev-parse HEAD == GITHUB_SHA
     // in actions/checkout@v1 this may not be true as it checks out the repository
     // using GITHUB_REF. There is a subtle race condition where
     // git rev-parse GITHUB_REF != GITHUB_SHA, so we must check